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Created page with "===3.2 Manufacturing of Semi-Finished Materials=== Semi-finished contact pre-materials can be manufactured from solid precious metals, precious metal alloys, or precious metal..."
===3.2 Manufacturing of Semi-Finished Materials===
Semi-finished contact pre-materials can be manufactured from solid precious
metals, precious metal alloys, or precious metal containing composite materials.
They are made in wire, strip, and profile form by known processing technologies
such as extrusion and subsequent annealing and drawing or roll-forming. They
are supplied following the manufacturer's internal standards usually related to
DIN EN specifications for copper based materials. The most important materials
are two – or multiple material layered semi-finished materials with the contact
material bonded in its solid phase to non-precious carriers by cladding, brazing,
or welding. The contact material can also be deposited on the carrier from the
liquid or vapor phase.
===3.2.1 Clad Semi-Finished Pre-Materials (Contact-Bimetals)===
Clad materials consist of two or more layers of different materials, the contact
material and the carrier, which are firmly bonded to each other. Depending on
the electrical requirements the contact material is mainly an alloy of gold,
palladium, or silver based while the carrier material are mainly copper alloys. To
bond these materials various technologies are utilized, the two most important
ones being described in more detail below.
During ''hot cladding'', the classic process, the materials to be clad are
assembled into a cladding package in block or plate form, heated to about
800°C and clad (or “welded”) together under high pressure ''(Fig. 3.3)''. At the
interface between the two materials a non-separable bond is formed by either
diffusion of the reaction partners or in liquid phase by forming a AgCu eutectic
alloy when an additional brazing alloy foil is placed between the two materials.
Further processing is done by rolling with required annealing steps between
subsequent thickness reductions. The disadvantage of this process is the
usually limited short length of final material strips.
Fig. 3.3: Hot cladding of pre-materials (schematic)
In the ''Cold Roll-Cladding'' process the bond between the contact and carrier
material is achieved by cold deformation of > 50% in one rolling pass ''(Fig. 3.4)''.
The high plastic deformation causes cold welding in the boundary layer between
the two materials. To increase the quality and strength of the bond a subsequent
diffusion annealing is performed in most cases. This process is most suitable for
clad semi-finished strips with thin contact material layers (> 2 μm) and large strip
length (> 100 m).
Fig. 3.4: Cold roll-cladding of semi-finished strips (schematic)
*Typical configurations of clad contact strips
bild
*Contact materials
bild
*Carrier materials
bild?
*Dimensions
bild
When specifying the contact material layer thickness it is recommended to use the
minimum required thickness.
*Quality criteria and tolerances
Strength properties and dimensional tolerances of clad contact bi-metals are
derived from the standards DIN EN 1652 and DIN EN 1654 for Cu alloys. When
specifying the width of the contact material layer it is recommended to use the
minimum required value. All dimensions should be specified originating from one
strip edge.
===3.2.2 Brazed Semi-Finished Contact Materials (Toplay–Profiles)===
The toplay process starts with a flat or profile – shaped contact material strip
which is fed together with the wider non-precious carrier material and in most
cases an intermediate thin foil of brazing alloy into a induction brazing machine
''(Fig. 3.5)''. An evenly distributed and reliable braze joint can be achieved this way
between contact and carrier materials. The combined material strip is rather soft
after the brazing process and re-hardened during a subsequent profile rolling
step. In this way different shapes and configurations can easily be achieved.
Fig. 3.5: Toplay brazing with an inductive heating inline equipment (schematic)
*Typical configurations of toplay contact profiles
bild
*Contact materials
bild
*Carrier materials
bild
*Quality criteria, dimensions and tolerances
bild
Strength properties and dimensional tolerances of toplay profiles are derived
from the standards DIN EN 1652 and DIN EN 1654 for Cu alloys.
===3.2.3 Seam–Welded Contact Strip Materials (FDR–Profiles)===
Seam–welding is the process by which the contact material in the form of a solid
wire, narrow clad strip, or profile is attached to the carrier strip by overlapping or
continuous weld pulses between rolling electrodes ''(Fig. 3.6)''. The weld joint is
created by simultaneous effects of heat and pressure. Except for the very small
actual weld joint area the original hardness of the carrier strip is maintained
because of the limited short time of the heat supply. Therefore also spring-hard
base materials can be used without loss of their mechanical strength. The use of
clad contact pre-materials and profiles allows to minimize the use of the costly
precious metal component tailored to the need for optimum reliability over the
expected electrical life of the contact components.
*Typical configurations of seam–welded contact strips
and stamped parts
bild
Fig. 3.6: Seam-welding process (schematic)
*Contact materials
bild
*Carrier materials
bild
*Dimensions
bild
*Quality criteria and tolerances
Strength properties and dimensional tolerances of toplay profiles are derived from the
standards DIN EN 1652 and DIN EN 1654 for Cu alloys..
===3.2.4 Contact Profiles (Contact Weld Tapes)===
Contact profiles span a broad range of dimensions. Width and thickness are typically
between 0.8 – 8.0 mm and 0.2 – 3.0 mm resp. Special configurations, often defined
as miniature-profiles or even micro–profiles can have a
width < 2.0 mm.
Miniature–profiles are mostly composed of a contact-bimetal material with the contact
material being a precious metal alloy or composite material clad, welded or coated by
electroplating or vacuum-deposition (sputtered) onto a weldable base material. Since
these profiles are attached to carrier strip materials usually by segment– or seam–
welding to the base materials, materials with good welding properties such as nickel,
copper-nickel, copper-tin, as well as copper-nickel-zinc alloys are used. The bottom
surface of the profiles usually has formed weld rails or similar patterns to ensure a
solid continuous metallurgical weld joint between the profile and the contact carrier.
Contact profiles in larger sizes are often used for switching devices in the low voltage
technology. For these the contact layer mostly consists of arc erosion resistant
materials such as silver–nickel, silver–metal oxides or the weld resistant silver–
graphite. The brazable or weldable underside of the metal oxide or silver–graphite
materials is usually pure silver with also quite often a thin layer of a phosphorous
containing brazing alloy applied to aid the welding process.
*Typical configurations of multi-layer contact profiles
bild
*Contact materials
bild
*Carrier materials
bild
*Brazing alloy
bild
*Quality criteria
Beause of the variety of configurations of contact profiles usually the quality
issues are separately agreed upon between the manufacturer and the user.
*Dimensions and tolerances
bild
The thickness of the Au top-layer, which is sputtered for example, is between 0.2
and 5 μm, depending on the requirements. Tolerance of thickness is about + 10%.
Semi-finished contact pre-materials can be manufactured from solid precious
metals, precious metal alloys, or precious metal containing composite materials.
They are made in wire, strip, and profile form by known processing technologies
such as extrusion and subsequent annealing and drawing or roll-forming. They
are supplied following the manufacturer's internal standards usually related to
DIN EN specifications for copper based materials. The most important materials
are two – or multiple material layered semi-finished materials with the contact
material bonded in its solid phase to non-precious carriers by cladding, brazing,
or welding. The contact material can also be deposited on the carrier from the
liquid or vapor phase.
===3.2.1 Clad Semi-Finished Pre-Materials (Contact-Bimetals)===
Clad materials consist of two or more layers of different materials, the contact
material and the carrier, which are firmly bonded to each other. Depending on
the electrical requirements the contact material is mainly an alloy of gold,
palladium, or silver based while the carrier material are mainly copper alloys. To
bond these materials various technologies are utilized, the two most important
ones being described in more detail below.
During ''hot cladding'', the classic process, the materials to be clad are
assembled into a cladding package in block or plate form, heated to about
800°C and clad (or “welded”) together under high pressure ''(Fig. 3.3)''. At the
interface between the two materials a non-separable bond is formed by either
diffusion of the reaction partners or in liquid phase by forming a AgCu eutectic
alloy when an additional brazing alloy foil is placed between the two materials.
Further processing is done by rolling with required annealing steps between
subsequent thickness reductions. The disadvantage of this process is the
usually limited short length of final material strips.
Fig. 3.3: Hot cladding of pre-materials (schematic)
In the ''Cold Roll-Cladding'' process the bond between the contact and carrier
material is achieved by cold deformation of > 50% in one rolling pass ''(Fig. 3.4)''.
The high plastic deformation causes cold welding in the boundary layer between
the two materials. To increase the quality and strength of the bond a subsequent
diffusion annealing is performed in most cases. This process is most suitable for
clad semi-finished strips with thin contact material layers (> 2 μm) and large strip
length (> 100 m).
Fig. 3.4: Cold roll-cladding of semi-finished strips (schematic)
*Typical configurations of clad contact strips
bild
*Contact materials
bild
*Carrier materials
bild?
*Dimensions
bild
When specifying the contact material layer thickness it is recommended to use the
minimum required thickness.
*Quality criteria and tolerances
Strength properties and dimensional tolerances of clad contact bi-metals are
derived from the standards DIN EN 1652 and DIN EN 1654 for Cu alloys. When
specifying the width of the contact material layer it is recommended to use the
minimum required value. All dimensions should be specified originating from one
strip edge.
===3.2.2 Brazed Semi-Finished Contact Materials (Toplay–Profiles)===
The toplay process starts with a flat or profile – shaped contact material strip
which is fed together with the wider non-precious carrier material and in most
cases an intermediate thin foil of brazing alloy into a induction brazing machine
''(Fig. 3.5)''. An evenly distributed and reliable braze joint can be achieved this way
between contact and carrier materials. The combined material strip is rather soft
after the brazing process and re-hardened during a subsequent profile rolling
step. In this way different shapes and configurations can easily be achieved.
Fig. 3.5: Toplay brazing with an inductive heating inline equipment (schematic)
*Typical configurations of toplay contact profiles
bild
*Contact materials
bild
*Carrier materials
bild
*Quality criteria, dimensions and tolerances
bild
Strength properties and dimensional tolerances of toplay profiles are derived
from the standards DIN EN 1652 and DIN EN 1654 for Cu alloys.
===3.2.3 Seam–Welded Contact Strip Materials (FDR–Profiles)===
Seam–welding is the process by which the contact material in the form of a solid
wire, narrow clad strip, or profile is attached to the carrier strip by overlapping or
continuous weld pulses between rolling electrodes ''(Fig. 3.6)''. The weld joint is
created by simultaneous effects of heat and pressure. Except for the very small
actual weld joint area the original hardness of the carrier strip is maintained
because of the limited short time of the heat supply. Therefore also spring-hard
base materials can be used without loss of their mechanical strength. The use of
clad contact pre-materials and profiles allows to minimize the use of the costly
precious metal component tailored to the need for optimum reliability over the
expected electrical life of the contact components.
*Typical configurations of seam–welded contact strips
and stamped parts
bild
Fig. 3.6: Seam-welding process (schematic)
*Contact materials
bild
*Carrier materials
bild
*Dimensions
bild
*Quality criteria and tolerances
Strength properties and dimensional tolerances of toplay profiles are derived from the
standards DIN EN 1652 and DIN EN 1654 for Cu alloys..
===3.2.4 Contact Profiles (Contact Weld Tapes)===
Contact profiles span a broad range of dimensions. Width and thickness are typically
between 0.8 – 8.0 mm and 0.2 – 3.0 mm resp. Special configurations, often defined
as miniature-profiles or even micro–profiles can have a
width < 2.0 mm.
Miniature–profiles are mostly composed of a contact-bimetal material with the contact
material being a precious metal alloy or composite material clad, welded or coated by
electroplating or vacuum-deposition (sputtered) onto a weldable base material. Since
these profiles are attached to carrier strip materials usually by segment– or seam–
welding to the base materials, materials with good welding properties such as nickel,
copper-nickel, copper-tin, as well as copper-nickel-zinc alloys are used. The bottom
surface of the profiles usually has formed weld rails or similar patterns to ensure a
solid continuous metallurgical weld joint between the profile and the contact carrier.
Contact profiles in larger sizes are often used for switching devices in the low voltage
technology. For these the contact layer mostly consists of arc erosion resistant
materials such as silver–nickel, silver–metal oxides or the weld resistant silver–
graphite. The brazable or weldable underside of the metal oxide or silver–graphite
materials is usually pure silver with also quite often a thin layer of a phosphorous
containing brazing alloy applied to aid the welding process.
*Typical configurations of multi-layer contact profiles
bild
*Contact materials
bild
*Carrier materials
bild
*Brazing alloy
bild
*Quality criteria
Beause of the variety of configurations of contact profiles usually the quality
issues are separately agreed upon between the manufacturer and the user.
*Dimensions and tolerances
bild
The thickness of the Au top-layer, which is sputtered for example, is between 0.2
and 5 μm, depending on the requirements. Tolerance of thickness is about + 10%.
